Software Growth

SaaS magic number

The SaaS magic number compares new recurring revenue to the sales and marketing spend that produced it. Around 1 means you can usually spend more on growth.

The magic number measures sales efficiency. It asks how much new annual revenue you got for each dollar you spent on sales and marketing in the previous period. If the answer is high, spending more on growth should pay off. If it is low, adding spend mostly adds cost.

How to calculate the magic number

There are slightly different versions. David Sacks uses net new ARR in the period divided by the prior period's sales and marketing expense. Tomasz Tunguz describes it as incremental annual revenue divided by sales and marketing investment.

Example: last quarter you spent $40,000 on sales and marketing. This quarter, recurring revenue grew by $8,000 per quarter, which annualizes to $32,000 of net new ARR.

You added 80 cents of annual revenue per dollar of spend. Using the prior quarter's spend accounts for the lag between spending and closing.

What good looks like

  • Sacks says ideally the ratio is above 1.
  • Tunguz reports that most public SaaS companies sit near 0.8, and that early-stage companies tend to look more efficient than mature ones as markets saturate.
  • Below 1, he suggests revisiting sales and marketing approaches or looking at upsell and cross-sell, and above 1 the company can invest more in growth.

Relation to CAC payback

Tunguz notes that the inverse of the magic number gives a payback period. In the example, 1 divided by 0.8 is 1.25 years of revenue to recover spend, about 15 months. That treats revenue as profit, so for a true payback use gross profit, as in CAC payback period. The two metrics measure the same idea from different ends.

Limits

  • It uses revenue, not margin, so a low-margin product can look efficient while it is not.
  • Churn matters. Use net new ARR, which subtracts churn, not just new bookings.
  • Long sales cycles need a longer lag than one quarter.
  • It is a company-wide average. Use CAC by channel for decisions about specific campaigns.

For small SaaS

With a handful of deals per quarter, a single customer can swing the number from 0.3 to 1.5. Calculate it on a trailing 12 months instead of a quarter, and count your own time in sales and marketing spend. For most bootstrapped products it is a sanity check, with payback and the burn multiple doing more of the work.

A caution on interpretation

A magic number above 1 does not mean you should spend blindly. It signals that, so far, each marginal dollar returned more than a dollar of annual revenue, but that can fall as you move from your easiest channels to harder ones. Raise spend in steps, remeasure after a full quarter or two, and stop if the ratio drops under about 0.7 or your CAC payback stretches beyond what your cash can carry.

Sources

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